The present invention relates generally to agricultural baling machines and more particularly to a baler for producing cylindrical bales, commonly referred to as round bales, having an improved wrapping apparatus for wrapping round bales of crop material formed in a bale forming chamber that reduces operating forces in the apparatus to improve durability.
Round balers generally have a bale forming chamber defined by a pair of opposing side walls associated with an array of side-by-side belts, transverse slats trained on chains, a plurality of transverse rolls or a combination of these various elements, e.g., rolls and belts. During field operation, windrowed crop material such as hay is picked up from the ground and fed in a continuous stream into a fixed or variable diameter chamber. The hay is rolled into a cylindrical package within the chamber, wrapped with twine, net or the like and ejected onto the ground for subsequent handling.
U.S. Pat. No. 5,289,672 and U.S. Pat. No. 4,956,968, issued to Underhill, disclose prior art round balers having a wrapping apparatus of the general nature described above. In this particular type of baler an expandable chamber is defined by a pair of fixed sidewalls, and a plurality of side-by-side belts cooperating with a series of transverse rolls, mounted between a pair of pivotally mounted arms. This arrangement of rolls and arms is commonly referred to as a sledge assembly. The chamber includes an inlet opening in the front through which crop material is fed. Also included is a pair of take up arms pivotally mounted on the main frame, between which arms a pair of guide rolls are journalled. A biasing force on the take up arms urges the outer surfaces of the guide rolls against the belts to maintain tension and thereby prevent slack from occurring in the belts during expansion and contraction of the chamber. Density of the bale can be affected by varying the force on the take up arms.
The present invention relates to an improvement in the wrapping system for round balers in which cylindrical packages of crop material (bale) are formed in a fixed or expanding chamber wherein one or more transverse forming rollers are employed. In such designs, a supply of wrapping material is typically dispensed from a supply area in the baler housing into the bale forming chamber through the space between two of the transverse rolls whereupon the wrapping material comes into contact with and adheres to the outer surface of the bale as it is rotated by the rolls. The wrapping system includes a wrapper insertion assembly which is pivotally connected to the baler and moved by an actuator. The insertion assembly is pivoted to move into a space between the two transverse rolls while gripping a free end of the wrapping material to feed the free end into the bale forming chamber and initiate the wrapping process. Once the wrapping material is engaged by the bale, the insertion mechanism is partially withdrawn as the bale is wrapped. Once the bale is completely wrapped, the insertion assembly is fully withdrawn and the wrapping material is severed from the supply.
Movement of a knife in the wrapping apparatus is coordinated by an interconnecting linkage whereby movement of the insertion mechanism positions the knife to sever the wrapping material at the appropriate time in the wrapping cycle. As the insertion mechanism pivots toward the wrapper insertion position, a cam in the mechanism guides a cam follower; a connected linkage actuates the knife, first moving it to a pre-cut position which stretches a spring to provide the cutting force and positions the knife linkage to restrain the knife against the spring force. As the insertion mechanism is fully withdrawn, the cam releases the knife and the spring moves the knife to sever the wrapping material.
The interconnecting linkage may be subjected to relatively high wear rates resulting from intermittent application of the relatively high forces necessary to coordinate motion of the knife, especially at the interface between the cam and the cam follower. Over time, the performance of the insertion mechanism and/or actuator may degrade as a result. It would be desirable to provide an improved mechanism that reduces operating forces in the wrapper insertion mechanism thereby improving the operational lifespan of the bale wrapping mechanism.